Extract mysql and postgresql drivers to plugins.

.gitignore

CMakeLists.txt

cmake/BuildSQL.cmake

debian/rules

include/config.h.cmake

include/lua/init.h

include/tarantool_plugin.h

src/CMakeLists.txt

src/admin.cc

src/admin.rl

src/box/lua/sql.lua

src/lua/init.cc

src/lua/lua_mysql.h

src/lua/lua_pg.h

src/lua/lua_sql.cc

src/lua/lua_sql.h

src/plugins/CMakeLists.txt

src/plugins/mysql/CMakeLists.txt

src/plugins/mysql/mysql.cc

src/plugins/pg/CMakeLists.txt